Localized electronic states of a terminated superlattice with a delta defect in the subsurface region

A Kronig-Penney-type model has been generalized to describe a semi-infinite GaAs/AlxGa1-xAs superlattice (SL), terminated by an AlyGa1-yAs substrate, and containing a single delta defect in the subsurface region. Analytical e xpressions for the energy of localized states, appearing inside the minigap s, have been derived using a direct multimatching procedure within an envel ope-function approximation. Numerical computations of the electronic struct ure have been performed for variable delta-defect position with respect to the SL surface and different-modelistic as well as realistic-values of the delta-function potential strength. Various SL surface conditions, correspon ding to the terminating potential barrier higher, equal, and lower than the SL barriers, have been considered. The obtained results indicate that both the energy spectrum and space-charge distributions of localized states can be tailored by an appropriate choice of the SL surface conditions (i.e., p arameters of the SL/substrate interface) and the parameters (the strength a s well as the position) of the inserted delta defect. [S0163-1829(99)08307- 1].